The present invention relates broadly to a flexible, high pressure reinforced, preferably thermoplastic hose construction, and more particularly to such a collapse-resistant or other hose construction which is especially adapted for use in offshore oil drilling applications or other harsh service environments.
Flexible high-pressure and ultra high-pressure hose is used in a variety of fluid transfer applications such as in oil field and offshore hydraulic applications. For example, in the recovery of crude oil from subterranean reservoirs, shale, or other formations, a substantial amount of oil may remain uncovered at the completion of primary recovery operations such as natural depletion. Secondary methods therefore often are used to increase the recovery yield. One of the more successful of these methods is that of miscible flooding wherein a solvent such as methanol is injected into the formation. The crude oil, which is miscible with the solvent, is displaced from the formation by the solvent and is extracted therewith from the formation. Secondary oil recovery methods are further described in U.S. Pat. Nos. 3,557,873; 3,637,015; 3,811,501; 4,299,286; 4,558,740; 4,605,066; 4,609,043; 4,678,036; 4,800,957; 4,899,817; and 5,632,336. Another such method is immiscible recovery wherein brine or water is substituted for the solvent.
In general, hoses adapted for solvent injection and other oil field applications not only must be flexible, i.e., kink resistant at a relatively small bend radius, but also must be capable of withstanding high and ultra high internal pressures and of being manufacturable in relatively long continuous lengths of 6000 feet (1830 m) or more. As used herein, xe2x80x9chigh-pressurexe2x80x9d is ascribed its common trade definition of hydraulic working pressures greater than about 1500 psi (10 MPa), with xe2x80x9cultraxe2x80x9d high being used herein to designate working pressures greater than about 15,000 psi (100 MPa) or more. For deep sea oil recovery and other underwater service, such hoses further must be capable of withstanding external pressures of 500-14000 psi (3.4-28 MPa) or more, be lightweight, and abrasion resistant, and for solvent injection applications additionally must be resistant to permeation by methanol or other solvents.
In basic structure, hoses of the type herein involved conventionally are constructed as having a tubular core surrounded by one or more reinforcement layers or courses of high tensile strength steel wire and/or synthetic fiber. The reinforcement layers, in turn, are protected by a surrounding outer sheath or cover which may be of the same or different material as the core tube. The cover also provides the hose with increased abrasion resistance.
The core tube, which may be a thermoplastic material such as a polyamide, polyolefin, polyvinyl chloride, or polyurethane, or a synthetic rubber material such as Buna-N or neoprene, is conventionally extruded and cooled or cured. As is detailed in U.S. Pat. Nos. 3,116,760; 3,159,183; 3,966,238; 4,952,262, if necessary, the tube may be cross-head extruded over a mandrel for support, or otherwise supported in later forming operations using air pressure and/or reduced processing temperatures.
From the extruder, the tube may be collected on a reel or other take-up device for further processing. As dispensed from the reel, the tube optionally next may be passed through an applicator for its coating with an outer layer of an adhesive material which, in the case of thermoplastic hose, may be a polyurethane or other isocyanate-based adhesive, or, in the case of xe2x80x9crubber,xe2x80x9d i.e., vulcanizable elastomeric, hose, a vulcanizable adhesion promoter. The core tube then may be delivered through a braider and/or a spiral winder for its reinforcement with one or more surrounding layers of wire and/or fibrous material such as a monofilament, yarn, or roving. These reinforcement layers, which are applied under tension and which may be bonded to the core and to adjacent reinforcement layers, typically comprise an interwoven braid or a spiral winding of a nylon, polyester, or aramid yarn, or a high tensile steel or other metal wire.
Following the application of the reinforcement layers, the outer cover or sheath optionally may be applied. Such cover, which may be formed as a cross-head extrusion or a spiral-wound wrapping, typically comprises an abrasion-resistant polymeric material such as a polyamide, polyolefin, polyvinyl chloride, or polyurethane. As before, an adhesive layer may be used to bond the outer cover to the reinforcement layers.
Representative high-pressure spiral wound and other hose constructions, as well as manufacturing methods therefor, are shown in U.S. Pat. Nos. 1,281,557; 3,566,924; 3,654,967; 3,682,202; 3,779,308; 3,790,419; 3,791,415; 3,805,848; 3,889,716; 3,890,181; 3,905,398; 4,000,759; 4,098,298; 4,175,992; 4,182,019; 4,241,763; 4,259,991; 4,294,636; 4,304,266; 4,317,000; 4,342,612; 4,343,333; 4,380,252; 4,384,595; 4,444,707; 4,456,034; 4,459,168; 4,463,779; 4,522,235; 4,537,222; 4,553,568; 4,585,035; 4,699,178; 4,850,395; 4,898,212; 4,952,262; 5,024,252; 5,062,456; 5,361,806; 5,698,278; and 5,778,940. Heretofore, however, it is believed that a high or ultra high pressure hose, that is, having a working pressure of 10 MPa or more, which was both flexible and highly collapse resistant, as well as resistant to solvent permeation, was unknown in the art. That is, although flexible high pressure hoses heretofore have been made collapse-resistant via, as is shown generally in U.S. Pat. No. 4,456,034, the incorporation of a helically-wound spring received internally within the core tube bore, it is believed that such springs would not be useful in conjunction with multi-layer core tubes which include an inner liner or barrier layer of a fluoropolymer or other chemically-resistant material. In this regard, there would exist at least the potential for the spring to wear through the barrier layer as the hose is subject to flexural forces. Such springs also are known to decrease with the flexibility of the hose, to introduce an objectionable flow restriction into the bore of the hose which is of particular concern as the length of the hose increases, to require a secondary operation for insertion, and to limit the continuous length in which the hose can be manufactured. Other constructions employing an armor instead of a spring similarly introduce a flow restriction and also result in a bend radius which is limited by the pitch of the armor.
In view of the foregoing, it will be appreciated that high pressure hose constructions must exhibit a demanding balance of mechanical and other physical properties for proper performance. Indeed, as commercial applications for high pressure hoses have increased as a less labor intensive and, therefore, more economical substitute for rigid metal pipe, there have been calls from industry for further improvements in such hoses and in the materials of construction therefor. Especially desired would be a construction which is flexible, yet resistant to external pressure collapse in critical applications such as deep sea oil recovery and oil field applications.
The present invention is directed to a flexible hose construction, and particularly to a reinforcement structure therefor, adapted for conveying fluids under relatively high internal working pressures of from about 15,000 psi (10 MPa) to about 15,000 psi (100 MPa) or higher which also is resistant to collapse at relatively high external pressures of between about 500-500-14000 psi (3.4-28 MPa), or from vacuum. Accordingly, the hose construction of the invention is particularly adapted for underwater oil recovery and other offshore applications, and may be used for both suction and discharge applications.
Advantageously, the hose of the present invention may include a structural collapse-resistant, shape-restoring element which is incorporated into the wall structure of the hose rather than being disposed internally within the hose bore. In this regard, the hose is constructed as including a tubular first elastomeric layer having a first inner radial surface and a first outer radial surface, and a tubular second elastomeric layer having a second inner radial surface and a second outer radial surface. A reinforcement helix, which may be a spiral of one or more ends of a monofilament steel or other metal wire, is wound over the first elastomeric layer as interposed between that layer and the second elastomeric layer. The element is spiral wound at a predetermined pitch angle to define a series of turns each being spaced-apart from an adjacent turn to define an interstitial area therebetween. The first and second elastomeric members each extends into the interstitial area with the first outer radial surface of the first elastomeric member being bonded, by fusion or other means, to the second inner radial surface of the second elastomeric member such that the helical reinforcement element is encapsulated therebetween. As encapsulated between the first and second elastomeric layers, the spring-like helical element is able to resist externally-imposed forces without elongating, compressing, flexing, or otherwise causing the hose to deform into an elliptical or other non-circular geometry. Moreover, the encapsulation of the helically-wound element additionally provides a smooth and efficient load transferring surface over which subsequent fibrous reinforcement layers may be braided or spiral wound to improve the internal pressure resistance of the hose.
In an illustrated embodiment, the hose construction of the present invention includes a tubular core over which the first elastomeric layer is superimposed, two or more fibrous reinforcement layers braided or wound over the second elastomeric layer to provide resistance to internal pressure, a primary cover surround the outermost reinforcement layer, and a secondary cover interposed between the innermost reinforcement layer and the outermost reinforcement layer. The secondary cover functions as an internal barrier against the ingress of sea water or other fluids should the primary cover be damaged or removed.
The present invention, accordingly, comprises the apparatus possessing the construction, combination of elements, and arrangement of parts which are exemplified in the detailed disclosure to follow. Advantages of the present invention include a hose construction which is light-weight, abrasion-resistant, and flexible, but which also performs under conditions of high internal and high net external pressures so as to be highly resistant both to kinking and to collapse from externally-imposed forces such as underwater pressure or from vacuum. Additional advantages include a collapse-resistant, high pressure hose construction which is manufacturable in relatively long lengths of 6,000-10,000 feet or more, and which further is particularly adapted for solvent flooding and other solvent transfer applications when used in conjunction with a composite core tube having an inner liner which is resistant to solvent permeation. These and other advantages will be readily apparent to those skilled in the art based upon the disclosure contained herein.